Apparatus for straightening woven material



June 30, 1942. T. M. BERRY 2,283,387

AiPARATUS FOR STRAIGHTENING WOVEN MATERIAL Original Filed April 22, 1938Apparatuls fbr' ampfifying autpuvf of phoo-e/cc'ric devices and farcharging cap a.cior

6'4 in accordance w/fh the difference in qwpub frequencies Inventor iTheodore M. Bert-y,

b M (J y His Attorney.

Patented June 30, 1942 APPARATUS FOR STRAIGHTENING WOVEN MATERIALTheodore M. Berry, Schenectady, N. Y., assignor to General ElectricCompany, a corporation of New York Original application April 22, 1938,Serial No.

Divided and this application December 29, 1939, Serial No. 311,537

(Cl. 17520J 4 Claims.

My invention relates to apparatus for straightening woven material, mypresent application being a division of my copending application SerialNo. 203,551, filed April 22, 1938, entitled Apparatus for straighteningwoven material. In the La Pierre et al., Patent 2,106,612 and in the LaPierre Patent 2,106,611 means are disclosed and claimed for detectingand correcting any skew that may be present in a moving strip of wovenmaterial thus straightening it. With apparatus such as that disclosed inthose patents, it has been found that under certain conditions thecorrecting mechanism sometimes had a tendency to oscillate or hunt to anobjectionable extent before coming to a final position at which the skewwas corrected.

My invention is designed to correct this objection by means of apparatuswhich is adapted to be substituted for certain parts of theapparatusdisclosed in the above mentioned La Pierre Patent 2,106,611. With theapparatus involving my invention when skew appears in the advancingstrip of woven material the correct ing means is operatedintermittently, that is, it alternately operates and remains at rest forbrief periods, the periods of rest serving to delay further correctionuntil the need thereof is found necessary. Moreover, the length of theoperating periods depends upon the amount of skew present. If, forexample, there is but a small amount of skew in the material theoperating periods will be short and the intervening rest periods will belong; conversely, if there is a large amount of skew present theoperating periods will be long and the rest periods short. Should theamount of skew detected in the advancing strip increase for any reasonnotwithstanding the operation of the correcting apparatus the length ofthe operating periods automatically increases and the length of the restperiods decreases. Likewise, if the amount of skew detected decreases asa result of the operation of the correcting apparatus or otherwise, thelength of the operating periods decreases or reduces to zero dependingupon the particular conditions present and the length of the restperiods increases. If, however, the detected skew decreases suddenly tosubstantially zero the straightening means will be operated briefly inthe reverse manner, thus in effect anticipating the probable arrival ofa reverse skew in the material.

In the above brief description I have used the term skew and shall useit hereinafter in a broad sense covering both that condition of the weftmembers of the material commonly spoken of as skew and as illustrated byFig. 4 of the aforesaid Patent 2,106,611 and that condition of the weftmembers commonly spoken of as bow and as illustrated by Fig. 5 of thatpatent. Since the skew may occur in either direction, the apparatuswhich I have devised is constructed to make the necessary correction foreither as in the aforesaid patent.

My invention will be better understood from the following descriptiontaken in connection with the accompanying drawing, and its scope will bepointed out in the appended claims.

Referring to the drawing which is a combined circuit diagram andfragmentary perspective view of apparatus illustrating an embodiment ofmy invention, the capacitor 64 is arranged to be given a charge of onepolarity or of the opposite polarity in accordance with the presence ofskew in one direction or the other in an advancing strip of wovenmaterial, the amount of the charge of either polarity being dependentupon the amount of skew being detected in the material. For giving thecapacitor 64 a charge in accordance with the character and the amount ofskew in the material, I may employ any known apparatus but preferably Iemploy the apparatus disclosed in the above-mentioned La Pierre Patent2,106,611 in which-the capacitor 64 corresponds with the capacitor 64 ofthe present application. For correcting skew in the material to therebystraighten it I may employ an known means such, for example, as thatshown in the aforesaid La Pierre et al. Patent 2,106,612 where therelative speeds of the two edges of the strip of woven material isvaried by the use of the reversible motor 41 acting through thedifferential connection with the tenter chains. Instead of the abovementioned apparatus I may employ the straightening means disclosed inthe aforesaid Patent 2,106,611 where the reversible motor 22 operatesthrough mechanism of a different type to effect the correction of theskew. In the present application the relays l6 and Ill take the place ofthe relays 69 and 10 of the patent. The skew detecting apparatus and theskew correctingapparatus disclosed in the aforesaid Patent 2,106,611 maybe briefly described as comprising the tenter chains 2 for moving thestrip of woven material I, the optical and photoelectric equipment 3;the skew correcting apparatus I, and the reversible motor 5 foroperating the same. The electrical apparatus for amplifying the outputof the photo-electric devices and for charging the capacitor 84 inaccordance l8, the resistance I4 and- IS. The resulting potentialdropthrough the 2 with the difference in the output frequencies of thosedevices is represented by the rectangle 5.

The charge given to the capacitor 64 and hence the average potentialdifference across it is proportional to the amount of skew in that partof the material passing the point at which the skew is being detected.Connected across the capacitor 64 whose capacitance, for example, may be.02 m. f., through the resistors I and 8, whose resistance may beone-quarter of a megohm each, isthe capacitor 9 whose capacitance,- forexample, ma be 1.0 m. 13., this circuit constituting a filter circuitwhich smooths out the rapid variations in the potential differenceacross the capacitor 64.

When there is no charge on the capacitor 9, the electron dischargedevices I and I0 each pass current through their anode circuits sumcientto operate t e relays II and II therein. Device ID passes currentbecause its grid is connected with its cathode through the resistors l2,l3 and I4 whose respective resistances, for example, may be 2 megohms,megohms and 2 megohms'. Likewise the device It passes current becauseits grid is connected with the oathode thereof through the resistors |2,l3 and I4 whose resistances also may be 2 megohms, 5 megohms and 2megohms'respectively. The relays and I I being energized, the windingsof the relays l8 and I6 are deenergized since they are arranged to besupplied from the source of current l5 through the back contacts of therelays II and II. The relay "5 is provided with-the 'two armatures l1and I8 which are arranged to act simultaneously and for this reason areshown tied toget er by a dotted line. The armature II controls onecircuit of the reversible motor by which it is caused to rotate in onedirection. The other armature l8 operates between the back con- ,tact I9which connects with one side of the capacitor 9 and the front contact 20which connects with the upper end of the resistor l3. Connected betweenthese two contacts is the capacitor 2| whose capacitance, for example,may be 0.5 m. f.

The relay l6 like the relay I6 has the two armatures I1 and I8, thearmature l1 serving to control the other circuit of the reversible motorby which the motor is caused to operate in the opposite direction andthe armature I8 operating between the back contact I9 and the frontcontact 20 connected respectively with the opposite side of thecapacitor 9 and the lower end of the resistor l3. Across these contactsis the capacitor 2| whose capacitance is the same as capacitor 2|. Othercapacitors 22, 23, 22 and 23 areemployed to filter out or absorb voltageimpulses ar isving from the operation of relays I6 and I6.-

ith no charge on the capacitor 9 the several relays will be inthe,position'illustrated'and the reversible motor 5 will be stationary.If an appreciable amount of skew is present in that part of the wovenmaterial passing the detecting means, the capacitor 9 will receive acharge which will be maintained substantially uniform by the apparatus las long' as the amount of skew re-' mains the same. Assuming that thischarge makes the upper plate" of the capacitor positive there will be acurrent flow through the armature I4, and the armature resistor M willmake the grid of the device l9 positive whereby the relay II is morestrongly energized. The potential drop'through'the"re sistor l4",however, will make the grid of the device |0 sufficiently negative to soreduce the ourrent flow therethrough that the relay II will open. Thisrelease of the relay II will cause the energization of relay IS. .Theresulting actuation of the armature II will close one circuit of thereversible motor whereby the motor will rotate in the proper directionto cause the straightening means driven thereby to correct the skew inthe material. By the actuation of the armature I8 the capacitor 2| isplaced in a circuit including the resistors l4 and I4 across thecapacitor 9 whereby it receives a charge from that capacitor. Thecharging of the capacitor 2| requires a certain time interval dependingupon its capacitance, the charge on capacitor 9 and the resistance ofthe resistors I4 and I4. It is during this time interval that the motor5 is operative. When the potential difference across the capacitor 2becomes nearly equal to that across the capacitor 9, the potential dropacross resistor I4 is insufficient to prevent the device It from passingenough current to operate the relay II. This relay therefore picks upits armature, thereby de-energizing relay I6. Upon the release of thisrelay the motor circuit 4 is opened whereby the straightening meansceases to function and the armature I8 by reengaging contact I9 allowsthe capacitor 2| to discharge through it and the resistor I3. Thepotential drop across the resistor I3 of the discharge current holds thegrid of the device I0 positive hence the relay II is maintainedenergized. When the capacitor 2| has discharged to a certain extent andthe discharge current thereof accordingly has become reduced to such avalue that the potential difference across the resistor l3 can no longerhold the grid of device l0 positive over the effect of the potentialdrop across resistor I4 due to the discharge current from capacitor 9,the grid of device l0 again becomes negative and the above mentionedprocedure is repeated.

As long as any skew is detected, the apparatus undergoes successivecycles'of operation like that described above and because of theresulting intermittent operation of the skew correcting apparatus 4,which comprises the load on the correcting system, that part of theapparatus connected between the capacitor 84 and the electron dischargedevices It and I0 functions as an antihunting means thus avoiding theaforesaid objection. The length of each cycle comprises an intervalduring which the capacitor 2| is receiving a certain amount of chargefrom the capacitor 9 and an interval during which the capacitor 2|discharges to a certain extent through the resistor l3. When the amountof skew detected is small and the charge maintained on the capacitor 9accordingly is small the charging intervals of the capacitor 2| areshort in comparison with the discharging intervals thereof, hence theperiods of operation of the straightening means are short in comparisonwith the intervals between those periods.

If a greater amount of skew is detected, a

greater charge is given to the capacitor 9 and the charging intervals ofthe capacitor 2| are "longer than before but the discharge intervals areshorter. Hence, with a greater amount of'skew the periods of operationof the straightening means are longer and the intervals betweenthose'periods are shorter; Likewise, if the amount of skew increases inspite of theeffort of the apparatus .to reduce it, the peri ds ofoperation of the straightening means increase in length and theintervals between those periods decrease in length or entirelydisappear.

The capacitor 2! Conversely ir the amount of skew decreases,

the amount of charge given to the capacitor 8 accordingly decreases andthe charging intervals 01 the capacitor 2| decrease while the dischargeintervals thereof increase. Hence, with a decrease in the amount of skewthe periods of operation ofv the straightening means decrease in lengthand the intervals between those periods increase in length. When thereis no longer any skew detected the with the relays in the positionsillustrated.

Sometimes the skew detecting means shows by its operation that amaterial amount of skew present suddenly decreases to substantially zeroand is immediately followed by a skew in the 15 opposite direction. Sucha condition has been found to exist when a seam is passed by which twolengths or the material are Joined end to end and particularly when carehas not been taken in making the seam to have on one'side thereofparallel to those on the other. When the straightening apparatus which Ihave devised encounters such a condition of reverse skew it appears toanticipate the demand for a quick readjustment of the straighteningmechanism and does it in the manner now to be described.

The sudden reduction of the first skew to a very small or zero value notonly releases the relay IS in the manner already described therebystopping the motor 5 but also starts the motor rotating in the oppositedirection in anticipation 01 a probable opposite skew to follow.

during the sequence of operations just described has, nevertheless,acquired a small charge by reason of the previous potential diiferenceacross the capacitor 9 and the grid current of the device IIJ. Thischarge it will be noted is such that the plate grid is negative. When,therefore, the charge on the capacitor 9 suddenly reduces to zero orapproximately so the grid of I is made suiiiciently negative by thecharge on the capacitor 2| to cause it to release the relay H and thus,acting 45 through the relay 56, to cause the motor, to operate in thereverse direction. 'I'he capacitor 2| soon becomes discharged, however,so the relay I! is actuated, the relay [6 is released and the motorstops unless the reverse skew condition or the following portion or thematerial causes the continued operation thereof.

In the above description, it has been assumed apparatus remains at rest10 the weft elements although substantially inactive of the capacitor 2|connected with the that the charge given to the capacitor 8 was of acertain polarity. Should this capacitor be given, instead, a charge ofthe opposite polarity in response to a skew in the opposite directionthe apparatus obviously will operate in a manner to cause the motordriving the straightening means to operate in the reverse manner tocorrect the opposite skew. In that case the grid of the device I 0 ismade negative, the relay II is released, the relay l6 is-energized andthe other motor circuit is energized all in the same manner as has beendescribed above in the case of the corresponding elements III, II and I6respectively.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In combination, a capacitor, an electroresponsive device, meanscontrolled by a charge on said capacitor for causing said device to havealternate periods of operation and non-operation, and means incooperation with said means for causing the length or the periods ofoperation to increase and the length of the periods of nonoperation todecrease in response to an increase in said charge.

2. In combination, a capacitor, an electroresponsive device constructedto operate in either of 'two opposite senses, means responsive to acharge on said capacitor for causing said device to operate in onesense, and means responsive to a sudden predetermined decrease insaidcharge for causing said device to operate in the opposite sense.

3. In combination, a capacitor, an electroresponsive device, meanscontrolled by a charge on said capacitor for causing said device to havealternate periods of energization and non-energization, and meansarranged to cooperate with said means for causing the length of theperiods of energization and the length of the periods ofnon-energization to vary inversely in response to a given change in saidcharge.

4. In combination, a capacitor, an electroresponsive device, meanscontrolled by a charge on said capacitor for causing said device to havealternate periods of energization and non-energization, and meansconstructed and arranged to cooperate with said means for causing therela-

